Characterization of African Bush Mango trees with emphasis on the differences between sweet and bitter trees in the Dahomey Gap (West Africa) Romaric Vihotogbe Thesis committee Promoters Prof.dr. M.S.M. Sosef Professor of Biosystematics Wageningen University / Naturalis Biodiversity Center Prof.dr. B. Sinsin Professor of Tropical Ecology University of Abomey-Calavi, Benin Co-promoter Dr. R.G. van den Berg Associate professor, Biosystematics Group Wageningen University Other members Prof.dr. K.E. Giller, Wageningen University Prof.dr. E. Smets, Leiden University / Naturalis Biodiversity Center Dr. T.R. van Andel, Leiden University / Naturalis Biodiversity Center Dr.ir. L. Visser, Centrum voor Genetische Bronnen Nederland The research was conducted under the auspices of the Research School Biodiversity. Characterization of African Bush Mango trees with emphasis on the differences between sweet and bitter trees in the Dahomey Gap (West Africa) Romaric Vihotogbe Thesis Submitted in fulfilment of the requirements for the degree of doctor at Wageningen University by the authority of the Rector Magnificus Prof.dr. M.J. Kropff, in the presence of the Thesis Committee appointed by the Academic Board to be defended in public on Thursday 1 November 2012 at 11 a.m. in the Aula. Romaric Vihotogbe Characterization of African Bush Mango trees with emphasis on the differences between sweet and bitter trees in the Dahomey Gap (West Africa), 189 pages. PhD thesis, Wageningen University, Wageningen, NL (2012) With references, with summaries in Dutch and English ISBN 978-94-6173-412-9 to Carole & Uriel Ronad Contents Chapter 1: General Introduction ............................................................................................. 1 Chapter 2: Ecological differences within African Bush Mango trees in tropical Africa with emphasis on the Dahomey Gap (West Africa) ....................................................................... 17 Chapter 3: Backgrounds of the domestication process of African bush mango trees (Irvingiaceae) in the Dahomey Gap (West Africa) ................................................................ 43 Chapter 4: Phenological diversity and distinction within African Bush Mango trees (Irvingia: Irvingiaceae) in the Dahomey Gap (West Africa) .................................................................. 83 Chapter 5: Morphological Characterization of African Bush Mango Trees (Irvingia species) in the Dahomey Gap (West Africa) ...................................................................................... 119 Chapter 6: Genetic diversity and difference within and between bitter and sweet African bush mango trees (Irvingia spp., Irvingiaceae) in West and Central Africa ........................ 147 Chapter 7: General discussion and conclusions ................................................................. 169 Acknowledgements ............................................................................................................. 176 Summary ............................................................................................................................. 179 Samenvatting ...................................................................................................................... 182 Curriculim vitae ................................................................................................................. 186 CHAPTER 1 GENERAL INTRODUCTION CHAPTER 111 General Introduction Romaric Vihotogbé Naturalis Biodiversity Center (section NHN), Biosystematics group, Wageningen University, The Netherlands & Laboratory of Applied Ecology; Faculty of Agronomic Sciences, University of Abomey-Calavi, Cotonou, Republic of Benin Background Biological diversity plays a key role (nutritional, medical, socio-cultural, ecological, etc.) in the sustainability of human life and is therefore the most valuable resource on earth (SCBD, 2000; Jose, 2012). It includes the variability of organisms as well as the ecological systems that provide the environmental conditions necessary for their continuous regeneration (Probst and Crow, 1991; Swingland, 2001). Moreover, genetic variations as well as morphotypes resulting from the interaction with the environment are an integral part of biological diversity (Probst and Crow, 1991; SCBD, 2000; Sarkar, 2002). Since the 1992 Rio de Janeiro Earth Summit, the recognition of the fact that the knowledge present within human communities related to the management and use of biological resources is inextricably connected to biological diversity conservation has significantly increased (Swiderska, 2006). Plants are a vital component of biological diversity and are central to human life, because they influence ecosystem resilience, soil stability and fertility as well as the agricultural systems on which human life depends (IPGRI, 1999; Eviner and Chapin, 2001). Among the large number of plant species valuable in human diets and other types of use, comparatively few contribute to the current exploitable agrobiodiversity (IPGRI, 1999). Agrobiodiversity includes the domesticated and cultivated plant species, and is defined by the Convention on Biological Diversity (http://www.cbd.int) as those plant species being manipulated during their evolutionary process in order to develop particular phenotypes that meet human needs. Among the limited set of domesticated / cultivated plant species, a comparatively low percentage have received adequate scientific attention with the intention to conserve their variability (Wood and Lenné, 1997). Many other valuable plants species are being collected from natural vegetations and integrated into the agricultural productive space 1 CHAPTER 1 GENERAL INTRODUCTION by local communities. The vast majority of the useful plant species from a variety of ecosystems are exploited only locally and are known to the scientific community under various names among which “plant non timber forest products (NTFPs)” remains the most commonly used one. Plant NTFPs in sub-Saharan Africa Plant NTFPs refer to the products (apart from timber) collected from wild plant taxa occurring in natural forests (SCBD, 2001; van Andel, 2006). They can also be harvested from wild species preserved by local farmers on farms in various traditional agroforestry systems (Tabuna, 2000). The evaluation of the diversity of tropical plant species exploited as NTFPs already started during colonial times (see Reede tot Drakestein, 1678-1693; Rumphius, 1741- 1750) and shows the very old symbiotic relationship between local communities and the environment (Irvine, 1952; Malaisse and Parent, 1985; Bergeret, 1986; Herzog, 1992; van Andel, 2000). This evaluation as well as the geographical areas covered are growing since the 1992 Rio de Janeiro Earth Summit which emphasizes the importance of the knowledge of local communities for the potential of biological resources (Hladik et al., 1996; Malaisse, 1997). The PROSEA and PROTA mega-programmes (http://proseanet.org/prosea/foundation.php, http://www.prota.org) are exemplary for such large-scale evaluations of botanical diversity resources in South-East Asia and Tropical Africa, respectively. Because plant NTFPs are increasingly being used, in-depth studies on different aspects of their use, production and resilience in natural ecosystems and their economic importance at local, regional, national, and international levels have become a priority research topic over the last few decades (Ruiz Pérez and Arnold, 1995; Arnold and Ruiz Pérez, 2001; SCBD, 2001; Rai and Uhl, 2004; Ticktin, 2004; Adepoju and Salau, 2007). It has become clear that plant NTFPs play a significant role in the daily lives of millions of rural as well as urban populations around the world (Tabuna, 2000). Particularly, 80% of the rural populations in sub-Saharan Africa depend on plant NTFPs for their health needs (Kalaba et al., 2010). Their biochemical and nutritional evaluations (many are rich in proteins, lipid, carbohydrates, minerals and various vitamins and fibers (Augustino et al., 2011)) have demonstrated their potential to resolve the growing food, nutritional and health crises in Africa (Okolo et al., 1995; Chadare et al., 2010; Ahenkan and Boon, 2011; Sossa- Vihotogbé et al., 2012). 2 CHAPTER 1 GENERAL INTRODUCTION Two decades ago, an evaluation of the contribution of plant NTFPs to local populations’ livelihood improvement was conducted throughout West and Central Africa by many organizations funded by the Consultative Group on International Agricultural Research (CGIAR). This evaluation intended to identify the key plant NTFP species on which research- development actions should be concentrated. It resulted in a great diversity of species including numerous multipurpose trees (Clark and Sunderland, 2004; Augustino et al., 2011). Even though there are many common types of use related to some species, geographically separated local communities not seldomly use them in different ways, in accordance with their culture, belief, food habits and traditional knowledge background accumulated through generations (Lesley and Brown, 2004; Sossa-Vihotogbé et al., 2012). However, human migration and nutritional interactions among societies can gradually reshape food habits and modify knowledge regarding the utility of the local plant biodiversity (Turner and Turner, 2008). Therefore, many species may become widely used across their natural distribution area or even transported, marketed and eventually cultivated beyond that. African bush mango trees (ABMTs) are one